In academia, and particularly in biological and medical research activities, among practically innumerable studies, experiments and laboratory examinations, a relatively small but frequently recurring interest has been shown in the use of light, in various different forms, as an investigative and/or diagnostic tool or instrumentality. A relatively primitive emanation of this interest is evidenced in the various forms of transillumination which have been experimented with and used in many different ways over a great many years, probably dating back into antiquity, and in general utilizing light relatively crudely, i.e., as a visual aid, to help produce visually-perceptible shadows, shapes and images within or upon what would otherwise be substantially opaque objects or surfaces. In other more complex procedures, light energy of particularly-selected parameters is impinged upon or injected into the subject matter to be investigated and interpreted from the standpoint of the quantity or nature of the light detectable at another location, typically opposite the point of injection. This approach frequently includes the use of spectrometers at the point of detection, and may or may not involve the use of particularly-selected wavelengths of light for application to the subject under study.
Thus, in earlier efforts utilizing basic transillumination, a typical approach would be to utilize a source of visible light coupled by a tubular shield or the like to a translucent body portion or object which is then viewed carefully from the opposite side with the human eye, often aided by various reflectors, magnifiers and the like. One immediately-available example of such a procedure is that utilized by physicians for examination of human sinus conditions. An example of the more complex type of procedure would be a scientific study such as for example is illustrated in scholarly publications of the type entitled "Infrared Microspectrum of Living Muscle Cells," by Darwin L. Wood (Science, Vol. 1, Jul. 13, 1951), in which different particular individual types of muscle fibers were placed between transparent plates and placed in the radiation beam of a microspectrometer, where they were subjected to various wavelengths of light up to about ten microns, with the detected transmission intensities being plotted according to wavelength. With respect to the efforts to use transillumination generally, further reference is made to publications such as that by M. Cutler, M.D., in the June, 1929, issue of Surgery, Gynecology and Obstetrics, entitled "Transillumination As An Aid In The Diagnosis Of Breast Lesions," and as to the more complex spectrophotometric procedures, reference is made to an article in the Aug. 5, 1949, issue of Science (Vol. 110), by Blout and Mellors, entitled "Infrared Spectra Of Tissues."
While the aforementioned article by Cutler discussed basic transillumination procedures for diagnosis of breast disease as early as 1929, a number of proposals for refinement and enhancement of the basic transillumination procedures have been suggested in intervening years. Thus, the use of color film was proposed in 1972 by Gros and Hummel, and Ohlsson et al. proposed in 1980 the use of infrared film rather than ordinary color film, both using visible yellow light as well as infrared or rear infrared light as the illumination. Carlson has further proposed the use of a Vidicon system as a detector or collector, but the ultimate analysis and interpretation is nonetheless done visibly.
In the area of spectrophotometric analytic and diagnosis efforts, infrared oximeters have been developed and utilized in relatively recent years for non-invasive monitoring of the oxygenation of blood in humans and other specimens, most typically by contact with the ear or finger extremity, a selected infrared wavelength being coupled to the involved body portion with detection occurring on the opposite side of such portion, variations in the light energy detected being directly indicative, after appropriate calibration, of the oxygen content of the blood flowing through the affected body portion, as a result of the known absorption references of particular infrared wavelengths by oxygenated hemoglobin. Somewhat analogous observations and/or phenomena may be discerned by contemplation of publications such as those by Blout and Mellors, noted above, which noted a dramatic increase in the intensity of light as the 9.3 micron band in cancerous breast tissue as compared to normal breast tissue and the proposed explanation that the 9.3 micron band is also one of the strong intensity bands for the enzyme ribonucleaes, which rapidly increases in amount in rapidly proliferating cancer cells.
Various publications of Frans Jobsis commencing in about 1977 and including U.S. Pat. Nos. 4,223,680, 4,281,645, 4,321,930 and 4,380,240 are based upon a somewhat analogous although specifically different reported phenomena, i.e., the spectrally distinctive absorption characteristics associated with the cellular enzyme cytachrome a, a.sub.3, which in turn is said to be integrally associated with, and indicative of, oxydative metabolism. On this basis, Jobsis proposed the use of a particularly-selected measuring wavelength and another carefully selected reference wavelength to produce apparent differences in detection level, which differences were said to demonstrate, and actually be indicative of, organ vitality or viability, since indicative of oxydative metabolism and therefore of oxygen sufficiency, the premise being that the chain of causation between the observed measurements and the body organ believed to be under investigation, i.e., internally subjected to the injected light, was complete and inclusive.